ENGINEERING  LIBRARY 


ENGINEERING  LIBRARY 


A  paper  to  be  presented  at  a  meeting  of 
the  International  Engineering  Congress, 
1915,  in  San  Francisco,  Cal.,  Septem- 
ber 20-25,  1915. 


[Advance  Copy.    Printed;  Not  Published.    For  Release  October  1,  1915.] 


WATER  WHEELS  OF  IMPULSE  TYPE. 

By 

W.  A.  DOBLE,  Mem.  Am.  Soc.  C.  E. 

Chief   Engineer,  Pelton  Water  Wheel   Co., 

San  Francisco,  Calif.,  U.  S.  A. 

INTRODUCTORY. 

The  modern  development  of  this  type  of  hydraulic  prime- 
mover  dates  back  to  the  "hurdy-gurdy"  water  wheel  constructed 
by  the  early  gold  miners  of  California.  The  history  of  the  wheel 
will  be  found  in  Volume  29,  1899,  Transactions  of  The  American 
Institute  of  Mining  Engineers,  Page  852, — "The  Tangential 
Water  Wheel". 

The  wheel  has  been  designated  by  several  different  names, 
viz;  "Impulse",  "Impulse-reaction",  "Free-jet",  "Spoon- 
wheel",  "Tangential"  and  "Pelton",  but  in  view  of  the  fact 
that  Pelton  developed  the  characteristic  dividing  wedge  of  the 
buckets,  and  was  the  first  to  develop  the  wheel  from  the  commer- 
cial standpoint,  the  engineering  world  has  adopted  the  name 
"Pelton  Wheel"  as  being  synonymous  of  the  type,  as  it  is  a  dis- 
tinct type  of  hydraulic  prime-mover,  differing  radically  in  prin- 
ciple from  the  pressure  types  and  the  various  forms  of  partial 
turbines  developed  in  Europe  and  in  the  eastern  part  of  the 
United  States. 

EARLY  DEVELOPMENT. 

In  considering  its  development  from  1850  to  1915,  it  will  be 
best  to  divide  this  time  into  two  periods.  First,  the  "Mining 
Period",  running  from  1850  to  1890,  during  which  time  the 
wheel  was  developed  primarily  by  the  miners,  and  its  principal 
use  was  in  connection  with  the  mining  industry.  Its  design  and 
development  were  restricted  in  merit  and  quality  by  the  rather 

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crude  requirements  of  the  mining  industry,  and,  of  course,  re- 
finements in  design  and  construction  beyond  the  requirements  of 
that  industry  were  not  justified.  The  power  of  each  wheel  was 
also  limited  to  comparatively  small  horsepower  output,  as  the 
nature  of  the  driven  apparatus  was  such  that  there  was  no  call 
for  large  power  output  from  a  single  wheel.  During  this  period 
the  effective  head  or  pressure  was  comparatively  low,  averaging 
from  200  to  500  feet.  The  power  developed  by  the  wheels  was 
necessarily  used  where  it  was  developed,  the  length  of  the  trans- 
mission being  limited  to  that  feasible  for  a  shaft,  belt,  or  rope 
drive. 

Second,  the  "Electrical  Period",  running  from  1890  to  date, 
during  which  period,  radically  new  and  severe  requirements 
were  demanded  from  the  makers  of  the  wheel.  The  size  and 
power  output  were  no  longer  limited  to  the  requirements  of  the 
immediate  location  of  the  wheel,  but  only  by  the  amount  of  power 
that  could  be  developed  by  the  water  available.  The  working 
head  was  greatly  increased,  as  new  conditions  justified  greater 
expenditures  in  the  development  of  the  water  shed,  with  its  stor- 
age dams,  conduits,  regulating  reservoirs  and  penstocks.  The 
problem  of  successful  speed  regulation  to  meet  the  requirement 
of  operating  two  or  more  dynamos  in  synchronism,  or  two  or 
more  widely  separated  power  plants  on  the  same  system  of  trans- 
mission and  distribution  also  arose,  and  involved  the  necessity 
of  a  governing  means  sufficiently  sensitive,  accurate  and  rapid  to 
maintain  a  uniform  speed  with  instantaneous  changes  of  power 
demand  from  zero  load  to  full  load  and  inversely,  and  with  fre- 
quent large  percentages  of  the  total  capacity  of  the  water  wheel 
instantly  rejected  or  applied. 

During  this  period,  a  further  requirement  developed,  viz., 
continuous  service;  whereas,  before  this  period,  continuous  ser- 
vice, and  all  that  it  means,  was  an  unknown  quantity.  Long 
distance  transmission,  reaching  out  over  wide  territories  and  sup- 
plying power  and  light  to  many  commercial  industries,  towns  and 
cities,  gave  an  entirely  new  meaning  to  the  term  continuous  ser- 
vice, and  demanded  apparatus  of  the  highest  type  of  engineering 
design,  material  and  workmanship,  to  meet  its  necessities. 

In  the  mining  age,  the  problem  of  speed  regulation  was  very 


simple,  since  the  early  use  of  such  wheels  was  principally  to  drive 
stamp  mills,  saw  mills,  etc.,  where  the  power  output  was  quite 
constant  and  the  friction  load  on  the  shafting  and  driven  machin- 
ery formed  a  large  proportion  of  the  power  developed.  In  such 
cases  regulation  was  accomplished  usually  by  partially  closing 
the  gate  valve  placed  back  of  the  nozzle  entrance,  or  as  a  refine- 
ment, in  wheels  using  a  rectangular  slot  nozzle,  a  sliding  tongue 
was  inserted  in  the  orifice,  that  could  partially  or  fully  open  the 
orifice.  A  refinement  for  wheels  using  a  circular  jet  was  the 
adoption  of  the  deflecting  nozzle,  to  permit  of  projecting  the 
entire  jet  against  the  buckets  of  the  wheel,  or  partially  or  wholly 
deflecting  the  jet  outside  the  path  of  the  buckets.  Other  improve- 
ments were  made,  such  as  in  using  cast  iron  instead  of  wood.  etc. ; 
but,  in  general,  it  is  reasonable  to  state  that  the  impulse  or  Pelton 
wheel  of  the  Mining  Period  was  comparatively  crude  in  its  engi- 
neering design -and  in  its  construction,  though  suitable  for  the 
work  it  was  called  upon  to  do.  Many  of  these  early  wheels  are 
still  in  use,  and  they  were  of  great  service  to  mankind. 

During  the  Electrical  Age  the  development  of  the  wheel  by 
modern  engineering  methods,  such  as  were  in  vogue  in  other 
types  of  prime-movers,  dates  back  to  the  first  work  in  long-dis- 
tance electric  transmission,  made  possible  by  the  invention  and 
development  of  the  static  transformer.  This  would  start  the  con- 
sideration of  this  later  development  with  the  years  1890-1893 
with  the  installation  of  the  Telluride  Power  Company's  Plant, 
the  justly  celebrated  Pomona  Plant,  and  the  plant  of  the  Red- 
lands  Electric  Light  &  Power  Co.  The  progress  in  the  art  from 
that  time  has  gone  hand  in  hand  with  a  similar  development  in 
the  co-related  work  of  the  electrical  engineer.  Thus  the  hydro- 
electric prime-mover  has  brought  about  a  great  and  rapid  de- 
velopment in  the  water  wheel,  with  its  accessories,  as  it  has  in 
the  development  of  the  dynamo.  A  similar  development  has  also 
taken  place  in  steam-electric  prime-movers.  New  problems  in  the 
designing  of  both  types  of  prime-movers — particularly  those  con- 
nected with  safety,  reliability  and  accurate  regulation — have  thus 
been  brought  about  by  the  special  requirements  of  the  electric 
dynamo,  with  the  co-related  problems  introduced  by  the  require- 


ments  of  long-distance  transmission,  continuous  service,  and 
speed  regulation  of  a  character  heretofore  unknown,  in  combina- 
tion with  the  demand  for  prime-movers  of  much  greater  power 
output,  high  rotative  speed,  and  to  operate  under  extremely  high 
heads  and  therefore  high  water  pressures. 

Tracing  the  development  from  1890-1833:  the  Telluride, 
Pomona,  Redlands,  and  the  other  early  hydro-electric  plants 
quickly  demonstrated  that  the  wheel  so  successful  in  the  Mining 
Period  was  entirely  inadequate  in  its  design,  material  and  work- 
manship to  meet  the  more  severe  requirements  of  the  hydro- 
electric generating  units. 

During  the  period  from  1890  to  date,  there  has  been  a  con- 
stant development  to  satisfy  the  more  and  more  severe  and  exact- 
ing demands  of  the  rapidly  growing  industry. 

To  establish  a  comparison :  in  the  plant  of  the  Telluride 
Power  Company  at  Ames,  Colorado,  installed  in  1890,  were  two 
hydro- electric  single-phase  units,  each  of  150  kw.  output,  con- 
sisting of  a  Pelton  wheel  directly  connected  to  a  Westinghouse 
generator.  These  wheels  operated  under  a  head  of  500  ft.  (152 
m.). 

In  the  Pomona  Plant  of  the  San  Antonio  Light  &  Power 
Co.,  Pomona,  California,  installed  in  1891,  were  two  hydro- 
electric single-phase  units,  each  of  120  kw.  output,  consisting  of 
a  Pelton  wheel  operating  under  a  head  of  402  ft.  (122  m.)  and 
directly  connected  to  a  Westinghouse  generator. 

In  the  Mill  Creek  Power  House  No.  1  of  the  Redlands  Elec- 
tric Light  &  Power  Co.,  near  Redlands,  California,  installed  in 
June  1892  and  first  put  into  operation  on  September  7,  1893, 
were  two  hydro-electric  three-phase  units,  each  of  250  kw.  out- 
put, consisting  of  a  Pelton  wheel  operating  under  a  head  of  295 
ft.  (90  m.)  and  directly  connected  to  a  General  Electric  gen- 
erator. These  were  the  first  three-phase  generators  made  in  the 
United  States,  and  this  was  the  first  three-phase  transmission 
system  to  be  put  into  service  in  the  United  States. 

The  development  since  these  early  installations  has  been 
very  remarkable,  as  will  be  appreciated  in  completing  the  com- 
parison with  the  more  recent  developments:  there  are  five  or 
more  power  plants  in  the  United  States  where  the  wheels  operate 


under  heads  of  approximately  2000  ft.  (610  m.)  and  over,  and 
in  Europe  one  plant  operating  under  a  head  of  2890  ft.  (880 
m. ) ,  and  one  plant  recently  completed  operating  under  a  head  of 
5250  ft.  (1720  m.),  wherein  a  single  jet  of  water  1%  inches  diam- 
eter develops  3000  horsepower.  The  increase  in  the  size  of  the 
units  is  more  striking,  starting  with  the  150-kw.  units  at  Ames  in 
1890  to  the  recent  generators  of  12,500  kw.  output  and  driven  by 
Pelton  wheels  of  20,000  hp.  capacity.  To  fully  appreciate  this 
development,  it  is  necessary  to  consider  that  it  is  the  result  of 
only  twenty-five  years'  work,  which  period  covers  the  entire  his- 
tory of  the  art  of  Hydro-Electric  Power  Generation  and  Trans- 
mission. 

The  details  of  design  of  each  hydraulic  prime-mover  are  con- 
trolled and  determined  by  the  natural  conditions  existing  at  the 
location  where  it  is  to  be  installed,  and  under  which  it  is  to  ope- 
rate. These  natural  conditions  and  limitations  differ  over  a 
wide  range  with  every  installation ;  therefore,  the  hydraulic 
prime-mover  cannot  be  standardized  in  design,  as  is  possible 
with  electric  generators,  steam  engines,  or  steam  turbines,  but 
each  prime-mover  must  be  specially  designed  and  developed. 

The  principal  controlling  factors  of  the  design  are :  ( 1 )  The 
water  quantity  curve,  or  the  quantity  of  water  available  during 
each  period  of  each  day  and  throughout  the  year;  (2)  the  total 
head  that  it  is  possible  or  profitable  to  develop ;  ( 3 )  the  presence 
of  satisfactory  sites,  favorably  located,  on  which  to  construct 
storage  reservoirs,  or  equalizing  reservoirs,  from  which  the  pres- 
sure pipes  will  carry  the  water  to  the  wheels ;  (4)  the  character  of 
the  load  curve  that  is  to  be  carried;  (5)  the  most  economic  speed 
of  rotation  of  the  electric  generator  or  driven  machinery;  (6) 
whether  or  not  riparian  or  irrigators'  rights  have  a  controlling 
interest  that  will  affect  the  possibilities  of  water  storage  during 
the  sag  in  the  daily  load  curve,  so  as  to  permit  the  water  not  re- 
quired during  this  sag  in  the  load  curve  to  be  conserved  and 
available  to  carry  the  peaks  of  the  load  curve.  These  conditions 
primarily  determine  the  general  type  and  capacity  of  the  instal- 
lation, the  number  and  capacity  of  the  separate  units  into  which 
the  plant  will  be  subdivided,  the  speed  of  rotation,  the  method 
of  speed  regulation  and  whether  or  not  water  economizing  meth- 


ods  can  be  used  to  an  advantage.  These  controlling  factors  differ 
so  materially  in  each  installation  that  they  not  only  affect  the 
general  type  or  arrangement  of  the  design  but  also  the  details. 

The  general  type  of  unit  to  be  adopted  in  a  given  power 
plant  will,  therefore,  be  determined  by  the  particular  arrange- 
ment and  characteristics  of  details  to  be  incorporated  in  the  unit, 
as  required  to  meet  the  conditions  under  which  the  prime-mover 
is  to  operate;  it  being  appreciated  that  there  are  in  practically 
every  prime-mover  certain  similar  details,  differing  only  in  size 
and  mode  of  operation. 

WHEEL  RUNNERS  AND  BUCKETS. 

The  term  "wheel  runner"  contemplates  the  entire  wheel 
proper,  consisting  of  some  form  of  center,  to  the  rim  of  which  the 
buckets  are  attached.  There  are  two  general  types  of  wheel  con- 
struction :  First,  the  Double-lug  buckets  j  secondly,  the  Chain- 
type  or  Triple-lug  bucket. 

The  double-lug  bucket  is  arranged  with  two  lugs  cast  inte- 
gral with  the  bucket.  The  wheel  center  consists  of  a  single  rim. 
The  two  lugs  of  the  bucket  are  accurately  machined  to  a  press 
fit  over  the  rim  of  the  wheel  center  and  the  buckets  are  held  in 
position  on  the  rim  of  the  wheel  center  by  two  bolts,  which  are 
pressed  into  reamed  holes  passing  through  the  two  lugs  of  the 
bucket  and  the  rim  of  the  wheel  center,  thus  making  a  very  sub- 
stantial construction.  This  type  of  wheel  is  shown  in  Fig  1  and 
the  photograph  of  the  De  Sabla  buckets  (Fig.  2). 

The  wheel  illustrated  in  Fig.  1  is  operating  under  865  ft. 
(264  m.)  head,  at  225  revolutions,  and  develops  3750  horsepower. 
This  wheel  is  constructed  with  a  forged  steel  disc,  which  is  car- 
ried on  a  cast-steel  hub  with  follower  plate. 

One  of  the  four  wheels  installed  in  the  Mill  Creek  No.  3  plant 
of  the  Southern  California  Edison  Company  furnishes  an  inter- 
esting illustration  of  the  double-lug  type  of  bucket.  This  wheel 
operates  under  1900  ft,  (580  m.)  head  at  430  revolutions  per 
minute,  developing  1600  horsepower,  and  has  been  in  continuous 
service  since  March  17,  1903.  This  wheel  held  the  record  for 
some  time  as  operating  under  the  highest  head  of  any  wheel  in 
the  world.  The  wheel  center  consists  of  an  annealed  open-hearth 


• 
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'  \    '  I          I       ; 

..:      1    ;.! 


Fig.  1.  Wheel  of  Double  Lug  Construction,  Puget  Sound  Power  Company. 
Wheel  center  made  from  steel  forging  bolted  to  a  wheel  hub  with  follower  plate. 
Develops  3750  hp.  under  865  ft.  (264  m.)  effective  head,  at  225  r.p.m. 

steel  casting,  the  buckets  being  of  special  hard  bronze.  This  type 
of  construction  is  thoroughly  satisfactory  for  all  installations 
where  the  ratio  between  the  diameter  of  the  jet  and  the  pitch 
diameter  of  the  wheel  is  favorable.  In  this  type  there  are  two 
bolts  for  each  bucket,  and  where,  owing  to  the  large  ratio  be- 


8 

tween  the  pitch  diameter  of  the  wheel  and  the  diameter  of  the 
jet,  there  is  ample  room  for  the  two  bucket  bolts  and  proper  lugs 
on  the  buckets,  this  type  of  construction  is  thoroughly  satisfac- 
tory. 

The  photograph  of  the  De  Sabla  wheel  (Fig.  2)  also  shows 
buckets  of  the  double-lug  type  of  construction.  This  photograph 
is  of  particular  interest,  as  it  shows  the  condition  of  the  buckets 
as  they  were  on  February  25,  1915,  the  wheel  having  gone  into 
service  October  22,  1903,  and  having  been  in  almost  continuous 
service  since  that  time  with  practically  no  expense  whatever  for 
maintenance.  The  construction  of  this  wheel  shows  a  forged 
nickel-steel  disc  4  inches  thick  at  the  rim  and  10  ft.  4  in.  in  diam- 
eter. This  forged  wheel-center  is  then  bolted  directly  to  a  flange 
forged  solid  with  the  hollow  nickel-steel  wheel  shaft.  The  buck- 
ets are  made  of  high-carbon  open-hearth  steel  castings.  This 
record  will  be  of  particular  interest  to  engineers  as  showing  what 
can  be  accomplished  in  the  way  of  durability  and  continuity  of 
service  from  a  properly  designed  "Pelton"  wheel.  These  wheels 
operate  under  1531  ft.  (467  m.)  head  at  240  revolutions  per  min- 
ute and  develop  3700  horsepower. 

The  chain  type  of  construction  differs  materially  from  that 
of  the  double-lug  construction.  In  the  chain-type  construction  a 
double  rim  is  required.  This  is  sometimes  made  of  a  wheel  with 
a  "U"-type  rim.  Generally,  however,  it  consists  of  two  separate 
wheel  centers,  the  hubs  being  so  finished  as  to  bring  the  space 
between  the  rims  of  the  two  wheels  a  proper  distance  apart.  The 
bucket  is  provided  with  three  lugs,  a  forward  center  lug  and  two 
rear  lugs.  Figure  3  shows  clearly  the  arrangements  of  the  lugs 
of  the  bucket.  Figure  4  shows  the  assembled  wheel  runner  com- 
plete. These  wheels  operate  under  1330  ft,  (405  m.)  head  at  360 
revolutions  per  minute,  and  each  wheel  develops  20,000  horse- 
power. 

In  this  design  the  center  or  forward  lug  of  the  bucket  is  a 
close  fit  between  the  two  rims  forming  the  duplex  wheel  center. 
The  two  rear  lugs  of  the  bucket  straddle  the  rims  of  the  wheel 
center,  the  spacing  of  the  lugs  of  the  bucket  and  the  drilling  of 
the  wheel  centers  being  so  designed  that  the  rear  lugs  of  one 
bucket  come  directly  in  line  with  the  for\vard  lug  of  the  next 


Fig.   2. 


Photograph  Showing  Condition  of  the  Buckets  on  No.  1  Water  Wheel  at  the 
De  Sabla  Power  Plant  of  the  Pacific  Gas  and  Electric  Company. 


This  wheel  operates  under  1531  ft.  (467  m.)  effective  head  at  240  r.p.m.  de- 
veloping 3750  hp.  It  was  first  put  into  operation  on  Oct.  22,  1903,  and  has  been  in 
almost  continuous  service  since  that  time  with  practically  no  expense  whatever  for 
maintenance.  This  photograph  was  taken  on  !•>!>.  25,  1915,  by  the  engineers  of  the 
Pacific  Gas  and  Klectric  Company  to  record  the  condition  of  the  buckets.  The  white 
spots  in  the  bowls  of  the  buckets  are  due  to  a  mineral  deposit  left  by  the  water  in 
the  buckets  in  drying.  The  entire  surfaces  of  the  buckets  are  smooth,  the  edges  of 
the  splitter  and  entrance  edges  as  shown  by  the  plv.>tograph.  being  sharp. 


10 

following  bucket,  these  holes  being  drilled  and  reamed  in  line.  A 
single1  bolt  therefore  passes  through  the  rear  lugs  of  one  bucket, 
the  double  wheel  rims  of  the  center  and  the  central  or  forward 
lug  of  the  next  following  bucket,  thus  connecting  up  all  of  the 
buckets  into  a  continuous  chain.  By  this  arrangement  it  will  be 
observed  that  there  are  the  same  number  of  bolts  as  there  are 
buckets,  though  each  bucket  is  secured  to  the  double  wheel  rims 
by  two  bolts. 

In  comparing  this  type  with  the  double-lug  type,  it  will  be 
observed  that  the  base  line  of  the  bucket,  or  the  distance  between 
the  supporting  bolts,  is  very  much  greater  in  the  chain-type  or 


Fig.  3.     Arrangement  of  Lugs  on  Chain  Type  or  Double  Lug  Type  of  Construction. 

triple-lug  buckets  than  it  is  in  the  double-lug  buckets.  This  type 
of  construction  is  particularly  suitable  for  all  installations  where 
the  ratio  between  the  diameter  of  the  jet  and  the  pitch  diameter 
of  the  wheel  is  small,  that  is,  where  a  large  diameter  of  jet  is 
applied  to  a  comparatively  small  diameter  of  wheel.  This  is 
always  the  case  where  a  very  large  power  output  is  required, 
with  a  turning  speed  comparatively  high,  as  proportional  to  the 
head  of  water,  thus  calling  for  large  buckets  on  a  compara- 
tively small  wheel.  It  is  also  especially  suitable  for  extreme 
cases  of  large  horsepower  and  high  heads,  making  the  wheel 
runner  of  the  most  stable  construction. 

In  the  construction  of  the  wheel  runners  for  comparatively 
low  heads,  cast- iron  wheel  centers  of  either  the  disc  or  "U"-rim 
type  give  good  results.  For  medium  high  heads,  wheel  centers  of 
either  the  disc  or  k'U"-rim  type  made  of  annealed  cast  steel  are 
thoroughly  satisfactory.  For  extreme  heads  and  large  horse- 
power output,  the  wheel  centers  should  be  made  from  chrome- 


11 


Fig.  4.  Wheel  of  Chain  Type  of  Construction.  Wheel  center  constructed  of 
two  separate  centers  with  hubs.  Similar  to  wheels  used  in  the  Drum  Power  Plant 
of  the  Paciic  Gas  and  Elect  is  Company,  developing  20,000  hp.  under  1330  ft. 
(405  m.)  effective  head  at  360  r.p.m. 

nickel  steel  forgings.  In  such  cases,  the  attaching  bolts  are  also 
made  of  heat-treated  chrome-nickel  steel  and  forced  into  place 
with  25  tons  pressure.  The  most  satisfactory  material  to  use  for 
the  buckets  is  a  very  high  grade  high-carbon  steel  casting.  For 


12 


the  highest  heads,  it  is  possible  to  use  drop  forgings  for  the 
buckets. 

In  the  construction  of  the  wheels,  the  accurate  dynamic  bal- 
ance of  the  structure  is  of  the  utmost  importance,  and  to  insure 
this,  the  buckets  are  balanced  in  a  special  apparatus  which  in- 
sures a  dynamic  balance  at  the  maximum  runawray  speed  of  the 
prime  mover. 

In  the  earlier  wheels  constructed,  the  breaking  off  of  the 
buckets  was  one  of  the  principal  sources  of  failure ;  also  the  great- 
est single  improvement  in  efficiency  of  the  wheels  was  secured  by 
the  development  of  the  ellipsoidal  type  of  bucket  bowls  illus- 
trated in  the  several  photographs,  this  change  alone  having  im- 
proved the  efficiency  of  the  wheels  by  over  10%. 

NOZZLES   AND   SYSTEMS   OF  CONTROL. 

In  general,  the  needle  type  of  nozzle  is  invariably  used, 
c  characteristic  jet  from  a  needle  nozzle  being  illustrated  in 
Fig.  5.  This  is  a  flash-light  photograph  taken  through  an 
opening  in  the  side  of  the  wheel  housing.  The  blur  at  the 
right  hand  side  of  the  wheel  represents  the  rapidly  revolving 
buckets  of  the  wheel ;  the  cone  in  the  center  of  the  jet  is  the 
end  of  the  needle  bulb.  A  characteristic  needle  and  nozzle  tip 
is  illustrated  in  Fig.-  6,  this  being  the  needle  and  nozzle  tip  for 
the  nozzle  shown  in  Fig.  7. 

The  determining  factor  in  selecting  the  type  of  needle 
nozzle,  which  also  carries  with  it  the  means  of  regulation  of 
the  power  output  and  speed  of  the  prime-mover  that  will  be 
used  in  a  given  plant,  depends  primarily  upon  whether  or  not 
water  economizing  control  can  be  used.  In  those  plants  that 
are  located  on  streams  where  water  storage  cannot  reasonably 
be  secured,  or  where  other  power  plants  are  located  on  the  same 
stream,  making  it  necessary  to  allow  the  full  flow  of  the  stream 
to  pass  the  plant,  or  on  those  streams  where  irrigators'  or  ripar- 
ian rights  have  a  prime  control,  thus  preventing  the  storage  of 
water,  the  simpler  stationary  needle-controlled  nozzle  with 
governor  deflector  control  over  the  jet,  or  the  needle-regulat- 
ing deflecting  nozzle  is  used.  The  stationary  needle-regulated 
jet-deflecting  nozzle  is  shown  in  Fig.  7  (a  jet  deflector  for  a 


Fig.  5.  Characteristic  Jet  from  Needle-Regulating  Nozzle.  Photograph  taken 
by  flash-light  through  opening  in  the  side  of  the  wheel  housing.  The  blur  at  the 
right  hand  side  of  the  photograph  showing  the  revolving  wheel,  the  cone  of  the 
needle  being  shown  clearly  in  the  center  of  ths  st:eam.  The  sha.p,  true  cylind.ical 
characteristic  of  the  jet,  its  transparency  and  absence  of  spraying  is  clearly  shown 
by  the  photograph. 


Fig.    6. 


Characteristic  Needle   and  Nozzle   Tip.     Needle  and   nozzle  tips  from   the 
nozzles  shown  in  Fig.  7.     Jet  10  yz  inches  in  diameter. 


14 


Fig.  7.  Stationary  Hand-controlled  Needle-regulating  Nozzle.  Arranged  for 
governor  control  through  the  means  of  a  jet  deflector,  this  nozzle  projecting  a  jet 
10 1/2  inches  in  diameter. 

nozzle  is  shown  in  Fig.  8).  The  nozzle  is  of  particular  interest, 
as  it  projects  a  jet  lO1/^  inches  in  diameter,  which  is  the  larg- 
est single  jet  of  water  used  at  the  present  time. 

Figure  8  illustrates  two  nozzles  of  this  type  arranged  to  be 
supplied  with  water  through  $  branch  "Y"  from  a  single 
pipe  line,  the  photograph  .clearly  showing  the  arrangement  of 
the  deflector,  the  hand-operated  needle  control,  and  the  needle- 
controlled,  reversing  water-motor-operated  gate  valves,  one  of 
which  is  bolted  to  each  of  the  two  discharge  flanges  of  the 
branch  "Y". 

The  method  of  mounting  the  jet  deflector  is  clearly  shown. 
The  jet  discharging  from  the  end  of  the  nozzle  passes  through 
the  cylindrical  bushing,  which  is  slightly  larger  than  the  jet. 
The  speed  control  is  secured  by  the  governor  operating  on  the 
rockshaft  and  swinging  the  deflector  more  or  less,  so  that  it  par- 
tially or  entirely  deflects  the  jet  outside  of  the  path  of  the 
buckets  of  the  wheel. 

The  needle-deflecting  regulating  nozzle  is  illustrated  in 
Fig.  9.  This  type  of  nozzle  consists  of  a  nozzle  body  which 


15 


If) 


Fig.  9.  Needle-regulating  Deflecting  Nozzle.  The  needle  regulation  is  by 
hand  control,  the  deflecting  of  the  nozzle  being  by  automatic  governor  control  with 
hydraulic  counterbalance  to  balance  the  weight  of  the  nozzle  and  the  contained  water. 

is  pivoted  to  a  ball  joint,  permitting  the  nozzle  to  be  raised  or 
deflected  so  as  to  either  direct  the  full  jet  into  the  buckets 
of  the  wheel  or  to  partially  or  entirely  direct  the  jet  outside 
of  the  path  of  the  buckets  of  the  wheel. 

In  both  the  stationary  needle  nozzle  with  the  jet  deflector 
and  the  needle-regulating  deflecting  nozzle,  the  needle  is 
usually  operated  by  hand  control,  the  needle  being  set  to  utilize 


17 

to  full  advantage  the  available  supply  of  water.  In  plants 
where  either  of  these  types  of  nozzles  is  installed  and  where 
there  are  forebay  reservoirs,  economy  in  the  use  of  water  is 
secured  by  setting  the  needle  at  different  times  during  the  day 
to  carry  the  maximum  load  on  the  plant,  the  needle  being  set 
to  follow  the  general  load  curve  of  the  plant,  while  the  momen- 
tary load  changes  and  speed  control  are  taken  care  of  by  the 
governor  either  operating  the  jet  deflector  or  deflecting  the 
nozzle. 

The  system  of  hand  setting  of  the  needle  with  governor 
control  of  the  deflecting  means  is  of  particular  value  in  semi- 
arid  countries  where,  due  to  the  influence  of  evaporation,  the 
daily  flow  is  variable  to  a  very  considerable  degree ;  and  also 
in  those  power  plants  where  the  source  of  water  supply  is  in 
the  snow  fields,  the  quantity  of  water  varying  to  a  very  great 
degree,  depending  upon  the  melting  of  the  snow  by  the  sun. 
In  such  plants  the  operator  can  set  the  needle  by  hand  at 
different  times  during  the  day,  to  utilize  to  the  best  advantage 
the  quantity  of  water  available. 

In  such  plants,  where  large  units  are  installed,  the  control 
of  the  needle  setting  is  by  means  of  an  electric  motor  with  re- 
mote control  from  the  switchboard,  so  that  the  power  plant 
operator  can,  from  the  switchboard,  set  the  position  of  the 
needle  so  as  to  carry  any  predetermined  load  that  is  desired, 
the  needle  setting  being  changed  from  time  to  time  as  the  gen- 
eral condition  of  the  load  changes.  In  such  plants  the  overall 
consumption  of  water  approximates,  in  a  series  of  steps,  the 
load  curve  on  the  prime-mover.  With  the  needle-regulating 
deflecting  nozzle,  the  weight  of  the  nozzle  with  its  water  con- 
tents is  counterbalanced  by  an  hydraulic  cylinder,  to  relieve 
the  governor  of  this  additional  weight,  though  the  inertia  due 
to  the  weight  of  the  nozzle  and  its  contained  water  must  be 
overcome  by  the  governor.  Both  the  stationary  type  of  nozzle 
with  jet  deflector  and  the  deflecting  nozzle  give  excellent  regu- 
lation, for  the  reason  that  there  is  no  change  in  the  velocity  of 
flow  of  the  water  in  the  pressure  pipe  line,  due  to  governor 
action.  Therefore,  very  sensitive  speed  regulation  can  be  main- 
tained, as  the  problem  of  inertia  and  the  time  of  acceleration 


18 

of  the  column  of  water  in  the  penstock  is  not  here  a  factor  in 
the  problem  of  speed  control. 

To  secure  a  better  economy  of  water  with  the  use  of  these 
types  of  needle  nozzles,  automatic  devices  have  been  developed 
so  that  the  governor  in  rejecting  the  load  on  a  plant  first  oper- 
ates the  deflecting  means  and  then  brings  about  a  following  and 
gradual  re-setting  of  the  needle  and  nozzle  opening.  However, 
these  complicated  arrangements,  at  best,  are  merely  adaptations 
and  approximations. 

The  ideal  type  of  nozzle,  and  one  that  has  been  used  in 
the  most  important  high-head  power  plants  where  sensitive 
speed  regulation  and  the  highest  economy  in  water  consump- 
tion is  required,  is  secured  by  the  needle-regulating  nozzle  with 
auxiliary  relief-nozzle  control,  as  illustrated  in  Figs.  10  and 
11.  In  general,  this  type  of  nozzle  consists  of  a  stationary  main 
nozzle  body,  the  power  jet  directed  against  the  water  wheel 
being  controlled  by  the  needle  of  the  main  nozzle.  This  needle 
is  direct  operated  by  the  speed  governor,  bringing  about  a  re- 
setting of  the  needle  for  each  change  in  power  demand  on  the 
prime-mover,  so  that  there  will  be  delivered  to  the  buckets  of 
the  wheel  at  all  times  just  sufficient  water  to  carry  the  load  on 
the  prime-mover,  thus  securing  a  water  consumption  by  the 
prime-mover  strictly  proportional  to  the  power  output  required 
from  it.  By  this  arrangement,  maximum  economy  in  the  use  of 
water  is  secured,  taking  advantage  of  every  sag  in  the  load 
curve  to  conserve  the  water  not  required  to  drive  the  wheel,  in 
order  to  have  this  water  available  to  carry  the  peak  loads. 

In  the  operation  of  this  type  of  nozzle,  to  insure  against 
water  ram  or  surges  in  the  pressure  pipe  line  arising  out  of  a 
sudden  reduction  of  load  on  the  prime-mover,  automatically 
bringing  about  a  correspondingly  rapid  contraction  of  the  noz- 
zle orifice  and  retardation  in  the  flow  of  water  in  the  pipe  line, 
an  auxiliary  relief  nozzle  is  provided,  which  is  directly  con- 
nected to  and  takes  its  water  out  of  the  body  of  the  main 
nozzle.  This  auxiliary  relief  nozzle  is  likewise  provided  with  a 
needle  control,  the  jet  from  this  auxiliary  nozzle  being  directed 
into  the  tail-race,  and  at  no  time  brought  into  contact  with  the 
wheel. 

The  movement  of  the  needle  of  the  auxiliary  relief  nozzle 


19 


is  inverse  to  that  of  the  needle  of  the  power  nozzle.  This  is 
clearly  illustrated  in  Fig.  10.  This  inverse  action  is  accom- 
plished by  means  of  the  controlling  lever,  one  end  of  which  is 
connected  to  the  operating  means  of  the  governor,  the  move- 
ment of  the  power  needle  being  secured  through  link  connec- 
tions between  the  cross-head  on  the  shank  of  the  power  needle 
and  the  controlling  levers.  The  lower  end  of  this  lever  is 


Fig.  10.  Typical  Arrangement  of  the  Needle-regulating  Nozzle  with  Auxiliary 
Relief  Control.  Shows  the  arrangement  of  the  lever  control  for  the  main  needle, 
and  control  of  the  relief  needle,  through  the  differential-cataract. 

attached  to  a  .cross-head  on  the  piston  rod  of  the  differential- 
eataraet,  which  is  attached  to  a  cross-head  on  the  stem  of  the 
needle  of  the  auxiliary  relief  nozzle.  These  levers  are  ful- 
erummed  between  the  1  wo  needle  connections.  It  is  evident, 
therefore,  assuming  that  the  differential-cataract  be  locked  in 
one  position,  that  a  closing  movement  of  the  needle  of  the 
power  no/xle  would  bring  about  a  corresponding  opening  of 
the  auxiliary  relief  nozzle,  and  vice  versa.  However,  such  an 
inverse  action  is  neither  required  nor  desirable,  as  it  would  not 
secure  the  desired  economy  in  the  consumption  of  water.  There- 
fore, the  differential-cataract  is  introduced  between  the  cross- 


20 


head  on  the  stem  of  the  needle  of  the  auxiliary  relief  nozzle 
and  the  lower  end  of  the  operating  levers. 

This  differential-cataract  is  so  adjusted  that  provided  a 
load  change  is  either  so  gradual  or  of  such  an  amount  as  not 


Fig.  11.  The  Nozzle  of  the  16,000  hp.  Units  being  Installed  in  the  Power 
Plant  of  the  Los  Angeles  Aqueduct.  Shows  arrangement  of  auxiliary-needle  relief 
control.  Movement  of  the  power  needle  and  the  auxiliary-relief  needle  is  controlled 
trom  a  central  governor  through  a  large  rockshaft  connecting  up  the  governor  with 
both  nozzles.  Hand  control  mechanism  is  provided  and  arranged  so  that  either  or 
both  nozzles  can  be  controlled  by  governor  or  by  hand.  This  nozzle  projects  a  jet 
8%  inches  in  diameter  under  870  ft.  (265  m.)  effective  head,  developing  16,000  hp. 
at  200  r.p.m. 

to  set  up  disturbances  and  excessive  pressure  rises  in  the  pres- 
sure pipe  line,  a  yielding  or  slipping  action  takes  place  in  the 
differential-cataract,  which  permits  the  auxiliary  relief  nozzle 
to  remain  closed.  Under  such  conditions,  therefore,  there  is  no 


21 

discharge  of  water  from  the  auxiliary  relief  nozzle.  In  case, 
however,  a  load  change  takes  place  which  brings  about  a  clos- 
ing movement  of  the  power  nozzle  of  sufficient  magnitude  to 
cause  excessive  pressure  rises  in  the  pressure  pipe  line,  or  where 
the  load  change  is  very  sudden,  which  would  bring  about  the 
same  results,  the  time  element  control  of  the  differential  cat- 
aract causes  the  auxiliary  relief  nozzle  to  be  opened  to  an 
amount  sufficient  to  prevent  such  pressure  rises.  Immediately 
the  closing  action  of  the  needle  of  the  power  nozzle  has  ceased, 
then  the  needle  of  the  auxiliary  relief  nozzle  commences  to 
close  at  a  rate  which  has  been  adjusted  and  which  will  not 
bring  about  objectionable  pressure  rises  in  the  pipe  line. 

The  performance  of  the  needle  nozzle  with  auxiliary  relief 
control  is  absolute,  the  movement  of  the  needles  of  the  two 
nozzles  being  from  the  same  prime-mover,  namely,  the  servo- 
motor of  the  governor.  This  gives  an  absolute  assurance 
against  accidents,  and  insures  the  maximum  water  economy  in 
the  operation  of  the  prime-mover  with  a  variable  load.  The 
movement  of  the  needles  in  the  two  nozzles  thus  interconnected 
and  operated  from  the  same  source  of  power,  insures  absolute 
safety,  higher  water  economy  and  is  more  reliable  than  a  gov- 
ernor-operated means  of  deflecting  the  jet,  and  an  indirect 
control  over  the  operation  of  the  needle. 

The  speed  regulation  secured  by  the  needle-regulating 
nozzle  with  auxiliary  relief  control  is  satisfactory  for  the  most 
exacting  conditions.  With  a  proper  proportioning  of  the  oper- 
ating elements,  an  absolute  control  is  secured  over  the  pressure 
rises  that  can  take  place  in  the  pipe  line  due  to  an  instan- 
taneous rejection  of  full  load  on  the  prime-mover,  which  would 
bring  about  an  instantaneous  closing  of  the  needle  of  the 
power  nozzle.  The  pressure  rises  can  be  kept  at  any  percent- 
age desired,  and  in  special  cases  a  negative  pressure  rise  can  be 
accurately  secured  with  instantaneous  closing  from  full  open- 
ing of  the  needle  of  the  power  nozzle. 

Fig.  11  shows  the  nozzles  for  a  double-overhung  type  of 
unit,  developing  16,000  horsepower.  These  nozzles  are  ar- 
ranged with  a  central  governor  control,  operating  the  nozzles 
of  the  power  and  auxiliary  relief  nozzles  through  the  rock- 
shaft  extending  between  the  two  nozzles.  Arrangements  are 


22 

made  for  independent  hand-control  of  the  needles  of  each  noz- 
zle, should  it  be  desired  to  operate  either  one  or  both  sides  by 
hand  control.  The  nozzles  illustrated  in  Figure  11  project  a  jet 
8l/±  inches  in  diameter,  the  head  of  water  at  the  plant  being 
940  feet. 

The  auxiliary  relief  nozzles  are  designed  to  secure  a  nega- 
tive pressure  rise  of  over  10%  with  an  instantaneous  rejection 
of  full  load  on  the  prime-mover.  The  negative  pressure  rise 
with  sudden  rejections  of  large  proportions  of  the  load  im- 
proves the  speed  regulation  of  the  prime-mover. 

The  latest  developments  in  large  prime-movers  equipped 
with  the  needle-regulating  nozzles  with  auxiliary  relief  control 
is  to  mount  the  servo-motor  of  the  governor  directly  on  the  power 
nozzle,  the  piston  of  the  servo-motor  being  mounted  on  the  stem 
of  the  needle  of  the  power  nozzle.  The  controlling  elements  and 
pendulum  head  of  the  governor  are  mounted  directly  on  the 
nozzle.  This  construction  is  illustrated  in  Figure  12.  A  com- 
parison of  the  design  in  Fig.  12  and  the  nozzle  arrangement  as. 
shown  in  Fig.  11  will  demonstrate  the  advantage  of  this  latest 
development. 

I  >y  the  arrangement  of  the  piston  of  the  servo-motor  of  the 
governor  directly  on  the  stem  of  the  needle  of  the  power  nozzle, 
the  most  sensitive  regulation  can  be  secured,  as  all  lost  motion 
and  delay  due  to  torsion  in  the  rockshafts  and  lost  motion  in  the 
connecting  elements  is  eliminated.  In  units  of  large  power,  this 
is  a  most  important  factor. 

GOVERNORS. 
/^ 

The  modern  governor  is  essentially  a  pressure  oil-operated 

'  device,  arranged  with  a  speed  sensitive  element,  a  servo-motor 
for  operating  the  regulating  elements,  pilot  and  relay  valves  to 
insure  a  quick  response  of  the  servo-motor  to  the  tendency  of, 

s^speed  changes  as  indicated  by  the  speed  sensitive  element.  Mod- 
ern governors  will  indicate  and  correct  speed  changes  of  from 
a/4  to  y<>  of  1%,  and  are  sensitive  to  a  degree  permitting  a  full 
stroke  of  the  governor  to  be  made  in  approximately  from  1% 
seconds  to  2  seconds  time. 

Governors  are  of  two  general  types:     One  where  the  gov- 


23 


24 

ernor  itself  is  a  completed  machine,  as  a  product  of  separate 
manufacture,  and  arranged  with  a  terminal  shaft  by  which  the 
gate  or  nozzle-operating  gearing  of  the  prime-mover  is  con- 
trolled and  operated.  Governors  of  this  type  are  practically  a 
stock  manufacture,  and  are  sufficiently  flexible  in  design  so  that 
they  can  be  satisfactorily  connected  up  to  medium  and  small 
size  units;  such  a  governor  is  illustrated  by  Fig.  13.  The  oil 
supply  for  this  governor  is  contained  in  the  base.  The  oil  pres- 
sure to  operate  the  servo-motor  is  secured  through  means  of  the 
gear  pump  shown.  The  speed  sensitive  element  operates  the 
pilot  valve,  which  in  turn  operates  the  relay  valve  which  controls 
the  oil  supply  to  the  cylinder  of  the  servo-motor.  The  servo- 
motor is  connected  to  a  terminal  shaft,  to  which  the  operating 
elements  of  the  prime-mover  are  connected.  The  character  of. 
regulation  secured  from  governors  of  this  type  is  thoroughly 
satisfactory  for  the  exacting  demands  of  hydro-electric  power, 
generating  stations. 

A  modification  of  this  type  of  governor  arranged  with  a 
vertical  terminal  shaft  is  illustrated  in  Fig.  14.  This  type  of 
governor  is  used  with  vertical  shaft  Pelton  wheels,  the  terminal 
shaft  of  the  governor  being  vertical  and  extended  to  the  wheel 
pit,  where  it  .operates  the  controlling  elements  of  the  unit.  It 
will  be  noted  that  this  governor  is  fully  enclosed,  the  speed  ele- 
ment being  mounted  at  the  top.  The  hand  wheel  at  the  side  is 
for  hand-control,  should  it  be  desired  at  any  time  to  operate  the 
prime-mover  in  this  manner. 

Governors  for  very  large  units  are  illustrated  in  Fig.  15, 
which  shows  what  is  termed  a  "direct-motion  governor",  com- 
plete with  its  independent  oil  pump,  oil-air-pressure  storage  tank, 
and  controlling  mechanism.  This  governor  has  a  capacity  of 
40,000  ft.-pounds,  the  speed  element  and  controlling  valves  being 
sensitive  to  a  degree  necessary  to  indicate  speed  changes  of  % 
of  1%.  Through  the  means  of  the  duplex  pilot  valve  and  relay 
valve  construction,  the  governor  can  be  adjusted  to  make  a  full 
stroke  in  less  than  I1/-)  seconds.  On  actual  test,  the  governor 
illustrated  made  a  complete  stroke  in  1.2  seconds  time.  How- 
ever, such  rapid  moving  governors  are  not  required  except  in 
extraordinary  cases.  The  principal  feature  of  the  design  of  this 


25 


Fig.   13.     Standard  Type  of  Oil-pressure  Operated  Self-contained  Governor. 


26 


Fig.  14.     Special  Type  of   Governor  Arranged  with  Vertical  Terminal  Shaft  to  be 
Used  in  Conjunction  with  Vertical-shaft   "Pelton"  Units. 


27 


Fig.  15.     A  New  Type  Direct-motion  Oil-pressure  Operated  Governor  of  40,000  ft.-lb. 
Capacity,  Complete  with  Independent  Oil  Pump  and  Oil-Storage  Tank. 


28 

governor  is  that  the  terminal  shaft  is  connected  directly  to  the 
oscillating  shaft  operating  the  gate  controlling  elements,  thus 
avoiding  lost  motion  due  to  linkage  connections.  To  secure  the 
rapid  action  of  this  governor,  large  oil  ports  are  required,  neces- 
sitating a  very  large  relay  valve.  This  is  taken  care  of  by  the 
duplex  pilot  valve  and  relay  valve  construction. 

The  most  recent  work,  however,  in  governing  apparatus  is 
the  direct  application  of  the  piston  of  the  servo-motor  of  the 
*i '..viTiior  to  the  end  of  the  stem  of  the  power  needle.  A  small 
governor  of  this  type  is  illustrated  in  Fig.  1.6,  this  governor  being 


Fig.   16.     Small  size   direct  motion  governor  mounted   directly   on  the  nozzle   body 
and  arranged  for  water  operation. 

designed  to  operate  with  water  pressure,  and  for  this  reason  a 
strainer  is  provided.  The  same  type  of  governor  is  also  arranged 
to  operate  from  an  independent,  oil  pressure  source.  Governors 
of  this  kind  give  excellent  regulation. 

A  modification  of  this  type  of  governor  is  illustrated  in  Fig. 
17,  which  shows  a  24-inch  Pelton  wheel  arranged  for  belt  drive; 
speed  and  power  control  of  this  unit  are  through  the  means  of 
the  governor  operating  a  jet  deflector,  the  needle  nozzle  being 
••out rolled  bv  hand.  A  modification  of  this  type  of  unit  is  illus- 


20 


Fig.  17.  A  Standard  "Pelton"  24-inch  Water  Motor  arranged  with  Oil- 
operated  Direct-motion  Governor.  Speed  and  power  output  of  wheel  controlled 
through  means  of  jet  deflector.  Motor  equipped  with  needle-regulating  nozzle 
hand  control. 

trated  in  Fig.  19,  which  shows  a  similar  wheel  direct  connected 
to  a  15-kw.  generator  mounted  on  a  continuous  bed-plate.  For 
units  of  this  small  size,  owing  to  the  insignificant  fly-wheel  value 
of  the  revolving  elements,  good  regulation  requires  the  mounting 
of  a  fly-wheel  on  the  shaft. 

Kxcellent  regulation  is  secured  from  these  small  units,  as 
will  be  noted  from  Fig.  18,  showing  a  tachograph  record  of  a 
test  mjide  on  the  unit  illustrated  by  Fig.  19.  The  four  upper 
charts  represent  the  speed  control  of  the  governor  when  instantly 
applying  and  rejecting  full  load  on  the  unit,  then  three-quarter 
load  on  the  unit,  and  then  one-half  load  on  the  unit.  In  con- 


30 


31 


Fig.  19.  "Pelton"  Hydro-Electric  Unit,  15  KW.  Capacity.  Arranged  with 
direct-motion  pressure  oil-operated  governor  operating  on  jet  deflector  with  needle- 
regulating  nozzle  hand  controlled.  This  type  of  unit  is  particularly  well  suited  for 
small  isolated  plants.  This  unit  operates  under  257  ft.  (78  m.)  effective  head, 
developing  20  hp.  at  1020  r.p.m. 

ducting  this  test  the  load  was  secured  by  a  water  rheostat,  the 
load  application  and  rejection  being  secured  by  opening  and 
closing  the  main  switch,  thus  bringing  about  an  instantaneous 
change  of  load  condition. 

A  further  test  on  this  unit  for  governing  was  carried  out  by 
removing  the  fly-wheel,  and  the  two  lower  charts  show  the  effect 
of  this  change. 

MAIN  SHAFTS. 

In  prime-movers  of  small  and  medium  size,  shafts  forged 
from  0.30  to  0.40  carbon  open-hearth  steel,  properly  annealed,  are 
thoroughly  satisfactory  for  the  purpose.  For  large  prime- 
movers,  however,  the  shafts  should  be  made  from  fluid-com- 
pressed, chrome-nickel  steel  ingots,  hollow  forged  and  oil  tem- 
pered. Shafts  of  this  type  have  now  been  in  continuous  service 
for  twelve  years.  They  have  proved  to  be  absolutely  satisfactory 
and  the  bearing  journals  have  taken  on  a  high  polish.  AYith  the 


32 


single-overhung  type  units,  it  is  preferable  to  provide  the  shaft 
with  a  flange  forged  solid  with  the  shaft,  the  wheel  center  being 
bolted  to  this  flange.  This  makes  a  thoroughly  reliable  construc- 
tion and  facilitates  erection  at  the  site  of  the  power  house.  With 
the  double-overhung  type,  at  least  the  wheel  runner  on  one  end 
must  be  pressed  on  to  the  shaft,  so  as  to  allow  the  shaft  to  be 
pressed  into  the  hub  of  the  rotor  of  the  generator;  otherwise  a 
very  expensive  shaft  design  must  be  provided,  with  an  enlarge- 
ment in  the  center  at  least  as  large  as  the  flanges.  This  con- 
struction is  not  usually  justified. 


MAIN  BEAEINGS. 

The  very  heavy  weight  of  the  revolving  parts  of  modern 
large  hydro-electric  prime-movers  together  with  the  high  surface 
speed  of  the  shaft  in  its  bearings  have  brought  about  a  develop- 
ment of  a  very  massive  high-speed  bearing.  Bearings  of  this 
type  are  illustrated  in  Figs.  20  and  21.  The  main  bearing  shown 
in  Fig.  21  is  constructed  for  a  shaft  diameter  of  20  inches,  with 


Fig.  20.  Heavy-pressure  High-speed  Bearings.  Shows  arrangement  of  lubri- 
cating-oil  rings,  and  the  construction  of  the  removable  revolving  shell.  Also  shows 
arrangement  of  water-cooling  tubes  through  oil  storage  in  base  of  bearing. 


33 


a  length  of  bearing  shell  of  69  inches,  the  total  weight  of  this 
bearing  as  shown  being  11,000  pounds.  This  is  one  of  the  bear- 
ings of  a  16,000  horsepower  unit  rotating  at  200  revolutions  per 
minute. 

The  bearing  surfaces  are  provided  with  oil  by  revolving  oil 
rings,  the  temperature  of  oil  in  the  bearing  base  being  controlled 
by  water-cooling  tubes.  In  addition,  provisions  are  made  for 


Fig.  21.  Typical  High-speed  Heavy-pressure  Bearings.  This  bearing  was 
constructed  for  a  shaft  diameter  of  20  inches,  with  a  length  of  bearing  shell  of  69 
inches.  Weight  of  bearing  11.000  pounds. 

supplying  fresh  oil  to  the  bearing  through  sight-feed  lubricators 
and  drawing  out  the  used  oil  through  an  overflow,  so  that  from 
time  to  time,  while  the  plant  is  in  operation,  the  oil  in  the  bear- 
ing can  be  withdrawn  and  replaced  with  fresh  oil  that  has  been 
filtered.  These  bearings  are  arranged  so  that  the  bearing  shells 
CMII  be  rotated  around  the  shaft  and  removed  without  lifting  the 
shaft  from  the  bearings.  They  arc  also  provided  with  air  seals 
at  the  end  of  the  bearing  to  prevent  leakage  of  oil  from  the  bear- 


a  a. 

i! 


al 


35 

ings.  Hinged  covers  are  provided  with  ample  sized  openings,  so 
that  the  operator  can  place  his  hand  directly  inside  the  bearings 
and  on  the  shaft,  to  check  the  temperature  and  condition  of  the 
bearing  surfaces.  Thermometers  are  also  installed  in  the  bear- 
ings to  indicate  the  temperature  of  the  film  of  oil  between  the 
surface  of  the  shaft  and  the  surface  of  the  bearing. 

A  further  control  of  the  temperature  of  the  bearing  is  also 
secured  in  large  units  by  discharging  a  small  spray  of  water 
through  the  hollow  shaft.  This  method  keeps  the  shaft  cool,  is 
thoroughly  satisfactory  and  efficient,  and  should  always  be  in- 
stalled on  the  largest  high-power  units.  The  arrangement  for 
applying  the  water  to  the  end  of  the  shaft  is  illustrated  in  Fig. 
12,  where,  at  the  end  of  the  shaft  opposite  to  the  water  wheel,  the 
spray  nozzle  is  shown.  Due  to  the  partial  vacuum  existing  in 
the  wheel  housing,  this  fine  spray  of  water  is  drawn  through  the 
shaft,  producing  thereby  a  most  efficient  cooling  medium. 

These  bearings  have  proved  to  be  absolutely  satisfactory 
under  the  most  severe  conditions  of  heavy  pressure  and  high 
speed.  The  older  form  of  so-called  spherical  self-aligning  bear- 
ings are  not  now  used  on  the  heaviest  type  of  units. 


WHEEL   HOUSINGS. 

The  general  type  and  construction  of  housing,  or  casing,  in 
which  the  wheel  is  to  revolve  is  illustrated  in  Fig.  22.  For  best 
practice  each  wheel  should  rotate  in  a  separate  housing  to  prevent 
interference  from  discharged  water.  The  lower  part  of  these 
housings  is  preferably  made  of  iron  castings,  the  upper  housing, 
or  cover,  being  preferably  made  of  steel  plate  riveted  into  a  cast 
iron  frame.  The  joints  in  this  plate  work  are  riveted  hot,  chipped 
and  caulked,  so  as  to  be  water-tight.  This  type  of  housing  for 
large  units  is  preferable  to  a  housing  made  entirely  of  cast  iron, 
as  it  is  lighter  to  handle  and  eliminates  any  danger  of  breakage. 
AVhore  the  shaft  of  the  water  wheel  passes  through  the  side  of 
the  housing,  leakage  of  water  through  the  opening  is  prevented 
by  means  of  a  centrifugal  disc  and  water  guard.  This  device 
makes  a  frictionless  packing.  In  small  units  it  is  preferable  to 
make  the  housing  of  cast  iron. 


36 


CONTEOL  GATES. 

A  very  important  feature  in  all  hydro  prime-movers  is  the 
main  control  gate  or  valve,  the  general  type  in  use  being  of  a 
single-disc  gate  construction.  In  the  earlier  plants  hand-operated 
gates  were  deemed  sufficient.  A  later  development  brought  about 
the  use  of  gates  operated  by  an  hydraulic  cylinder,  as  shown  in 
Fig.  35  of  the  Crane  Valley  No.  1  Power  Plant.  The  latest  de- 
velopment in  disc  gate  valves  is  where  the  gate  disc  is  operated 
by  a  reversible  water  wheel.  A  gate  of  this  type  is  illustrated  in 
Fig.  23.  This  type  of  gate  has  proved  more  reliable  and  satis- 
factory in  service  than  the  hydraulic- cylinder  operated  gate 
valve,  as  grit  and  foreign  substances  in  the  water  which  have  a 
tendency  to  clog  the  valves  and  cylinders  of  hydraulic-cylinder 
operated  gate  valves  do  not  affect  the  operation  of  the  reversible 
water  motor. 

Furthermore,  the  reversible  water  motor  has  a  very  heavy 
starting  torque,  which  is  of  value  in  commencing  the  opening 
stroke  of  a  gate  valve  which  may  have  remained  shut  for  some 
period  of  time,  as  in  such  cases  there  is  a  tendency  for  a  gate 
disc  to  stick  to  its  seat. 

In  the  reversible  water-wheel  operated  gate  valve,  the  main 
gate  stem  is  provided  with  a  safety  limit  stop,  so  that  in  the  open- 
ing or  closing  movement  of  the  gate  it  protects  the  gate  against 
stress  which  would  be  set  up  in  the  structure,  due  to  over-opening 
or  over-closing  the  gate  by  careless  operation. 

For  prime-movers  operating  under  the  highest  heads  and 
where  the  units  are  of  very  large  power  output,  the  disc  gate 
valve  is  not  the  best  form,  owing  to  the  enormous  pressure 
brought  upon  the  seats  of  the  gate  ring  and  to  the  cutting  action 
on  these  seats  due  to  eddy  currents  set  up  in  the  water  passing 
through  the  throat  of  the  gate. 

The  ideal  type  of  control  gate  for  use  with  the  largest  size 
units  and  under  extremely  high  heads  is  the  "uniform-flow 
needle  gate  valve"  illustrated  in  Fig.  24.  In  the  control  of 
water  under  high  heads,  it  has  been  demonstrated  that  the  needle 
type  of  valve  is  the  proper  design  to  adopt.  The  construction,  as 
shown  in  Fig.  24,  consists  primarily  of  a  needle-regulating  valve 


37 


Fig.  23.     Single-disc  Type  Gate  Valves,  Operated  by  Reversible  Water  Motors. 


38 


controlled  by  an  hydraulic  cylinder,  with  a  terminal  slow-closing 
safety  element.  This  slow-closing  safety  element  consists  of  an 
extension  of  the  piston  rod  which  passes  into  a  labyrinth  in  the 
cylinder  head.  The  closing  of  the  valve  is  permitted  to  take  place 
by  discharging  the  pressure  fluid  from  this  cylinder.  As  the 
valve  approaches  the  closing  position,  the  extension  stem  enters 
the  labyrinth  shown,  and  gradually  restricts  the  escape  of  fluid 
from  the  cylinder.  This  resistance  effect  is  cumulative,  so  that 
absolutely  no  shock  or  jar  can  be  brought  on  the  pipe  line. 


Fig.  24.     Uniform-flow   Needle   Gate   Valves    Designed  for   the   Largest   Size   Unitg 
Under  Extreme  Conditions  of  Head. 

From  the  design  it  will  be  observed  that  owing  to  the  uni- 
form flow  through  the  valve,  no  eddy  currents  can  form.  The 
seat  is  of  such  form  that  the  water  flows  smoothly  over,  prevent- 
ing the  cutting  out  due  to  eddies  forming  in  the  disc  type  of  gate 
valve.  This  type  of  gate  valve  can  also  be  inspected.  This  is 
provided  for  by  the  telescopic  section  of  the  valve  body  which 
can  be  drawn  back  into  the  pipe  line,  permitting  inspection  with- 


39 


Fig.   25.      "Ensign"  Vortex  Baffle  Plate. 

out  disturbing  any  of  the  parts  supported  by  the  foundations. 
By  this  method  a  complete  inspection  and  replacement  of  all  of 
the  working  or  wearing  parts  of  the  valve  can  be  made. 

It  will  be  observed  that  a  by-pass  valve  is  arranged  so  that 
under  normal  operating  conditions  the  main  valve  would  be 
opened  with  an  equilibrium  of  pressure  on  both  sides  of  the 
valve.  However,  it  is  designed  and  constructed  so  that  in  case 
of  emergency  the  valve  can  be  safely  opened  with  the  full  pres- 
sure of  water  on  one  side.  This  type  of  valve  incorporates  in  its 
design  and  construction  the  elements  that  are  essential  for  a  safe 
and  satisfactory  operating  valve  under  the  most  extreme  condi- 
tions of  high  pressure  and  large  power  units. 

BAFFLE  PLATES. 

With  prime-movers  operating  under  high  heads,  it  is  neces- 
sary to  provide  some  device  to  bring  to  rest  the  water  discharged 
from  the  deflecting  nozzle  when  the  jet  is  deflected  from  the 
wheel,  also  to  take  care  of  the  discharge  of  the  auxiliary  relief 
nozzles  where  this  discharge  cannot  take  place  through  a  free 


40 


channel.  This  problem  is  an  extremely  difficult  one,  but  has  been 
most  satisfactorily  solved  by  the  ' '  Ensign  Vortex ' '  type  of  baffle 
plate,  illustrated  in  Fig.  25.  The  action  of  this  baffle  plate  is 
similar  to  that  of  the  Pelton  bucket,  excepting  that  the  discharge 
instead  of  leaving  the  sides  of  the  bucket,  is  brought  through  an 
angle  of  approximately  270  degrees,  so  that  the  water  expends 
its  energy  in  discharging  against  itself.  These  baffle  plates  have 
been  tested  out  under  heads  of  water  of  over  2000  ft.  (600  m.) 
and  are  absolutely  successful  in  destroying  the  velocity  in  the 
water  without  commotion,  and  show  practically  no  signs  of  wear. 
The  original  baffles  of  this  type  were  installed  in  the  Mill  Creek 
No.  3  Plant  of  the  Southern  California  Edison  Company,  which 
was  started  March  17,  1903,  operating  with  1900-ft.  (580  m.) 
head,  the  wheels  developing  1600  horsepower.  These  baffles  are 
in  service  today  and  show  practically  no  indication  of  wear. 

TYPES  OF  DESIGN. 

In  general,  the  most  favorable  design  of  hydraulic  prime- 
mover,  where  the  conditions  of  installation  permit,  is  the  single- 
overhung  horizontal-shaft  type,  the  general  arrangement  being 


Fig.  26.     Characteristic    Type    of    Exciter    Unit   Used   on  Large   Plants.      Operates 
under  360  ft.    (110  m.)   effective  head  at  720  r.p.m.,  developing  44  hp. 


41 


Fig.    27.      Small-size   Wheel  with  Direct-motion  Governor   Mounted   on   Nozzle   Body 
and  Controlling  the  Needle  Direct. 

effected  by  a  modification  of  the  detail  elements,  such  as  regulat- 
ing elements,  etc.,  and  their  mode  of  operation. 

Figure  26  illustrates  an  exciter  unit,  consisting  of  a  Pelton 
wheel  driving  a  direct-current  exciter  and  an  induction  motor, 
the  power  output  of  the  wheel  being  regulated  by  a  hand-con- 
trolled needle  nozzle.  In  the  operation  of  such  a  unit,  sufficient 
water  is  discharged  against  the  wheel  to  carry  somewhat  more 
that  the  excitation  load  on  the  generator.  This  causes  the  induc- 
tion motor  to  act  as  a  generator,  discharging  into  the  main  bus 
bars  to  which  the  induction  motor  is  connected.  This  induction 
motor  acts  as  a  speed  control,  in  that  it  rotates  practically  in 
synchronism  with  the  main  generators,  but  has  the  advantage  of 
sonic  slip,  so  that  speed  variation  on  the  main  unit  is  modified 
due  to  the  slippage  of  the  inductor  generator  and  to  the  fly-wheel 
value  of  the  revolving  elements  of  the  exciter  unit. 

A  further  advantage  of  this  type  is  that  in  case  of  interfer- 
ence, such  as  clogging  of  the  water-wheel  nozzle,  which  would 
otherwise  bring  the  exciter  to  rest,  immediately  that  the  power 


42 


developed  by  the  water  wheel  begins  to  fall  off,  the  induction 
motor  carries  the  exciter  unit.  This  type  of  exciter  is  now  being 
installed  in  the  largest  hydro-electric  stations  and  has  proven 
thoroughly  satisfactory  for  the  purpose. 

A  type  of  Pelton  wheel  arranged  for  exciter  drive  and  pro- 
vided with  a  direct-motion  governor  mounted  directly  on  the 
nozzle  is  illustrated  in  Fig.  27.  This  type  of  unit  is  also  used 
for  small  isolated  plants. 

An  hydro-electric  unit  suitable  for  small  plants  is  illustrated 
in  Fig.  28.  This  shows  an  ideal  two-bearing  single-overhung 
unit,  the  revolving  element  of  the  generator  being  mounted  be- 
tween the  bearings,  the  water  wheel  being  mounted  on  one  end 
of  the  shaft  overhanging  one  bearing,  and  the  fly-wheel  being 
mounted  on  the  opposite  end  of  the  shaft,  overhanging  the  oppo- 
site bearing.  This  unit  contains  a  direct-motion  governor,  ope- 


Fig.  28.  Typical  Single-overhung  Horizontal-shaft  Type  Unit  for  Small  Isolated 
Plants,  Plantation  Work,  etc.,  Speed  control  is  by  means  of  a  direct-motion  governor 
o::e.-ating  directly  on  the  controlling  needle.  Operates  under  90  ft.  (27.5  m.)  effective 
head  at  350  r.p.m.,  developing  18  hp. 


Fig.  29.  Typical  Hydro-electric  Unit  for  Installation  in  Small  Power  Plants. 
Arranged  with  needle-regulating  nozzle  hand  control,  with  governor  operating  de- 
flecting jet.  Operates  under  584  ft.  (178  m.)  effective  head  at  600  r.p.m.,  develop- 
ing 300  hp. 

rating  the  needle  direct.  In  addition,  there  is  an  auxiliary  hand- 
control,  should  it  be  desired.  Units  of  this  type  are  particularly 
well  adapted  to  small  isolated  power  plants,  such  as  on  planta- 
tions and  for  small  towns. 

In  installations  where  it  is  not  desirable  to  vary  the  quantity 
of  water  by  the  governor  operating  directly  on  the  needle,  the 
jet-deflecting  control  is  used.  A  medium-sized  unit  with  this 
type  of  control  is  illustrated  in  Fig.  29.  With  this  unit  the  set- 
ting of  the  needle  is  done  by  hand,  the  momentary  speed  control 
being  secured  by  the  governor  operating  the  jet  deflector;  units 
of  this  type  ranging  in  size  from  100  horsepower  to  1000  horse- 
power are  very  satisfactory  in  service. 

An  hydro- electric  unit  of  medium  size  and  involving  the 
most  advanced  construction  is  illustrated  in  Fig.  30.  In  this 
unit  it  will  be  noted  that  the  speed  governor  is  incorporated 
within  the  nozzle  construction,  and  the  unit  is  further  equipped 
with  the  needle-control  auxiliary  relief  type  of  nozzle.  The  unit 
is  arranged  with  two  main  bearings,  the  revolving  element  of  the 


44 


generator  being  placed  between  the  bearings,  the  water  wheel 
being  mounted  on  one  end  of  the  shaft  and  the  fly-wheel  on  the 
other.  The  entire  unit  is  mounted  on  a  combined  heavy  cast-iron 
base,  securing  thereby  a  most  rigid  construction.  This  unit  in- 
volves all  of  the  improvements  of  the  highest  grade  large  power 
units. 

In  the  medium  and  larger  sized  units,  cast-iron  base  plates 
are  neither  necessary  nor  desirable,  owing  to  the  very  heavy  first 
cost  and  weight ;  and  furthermore,  as  in  all  large  units,  it  is  neces- 
sary to  depend  upon  the  stability  of  the  foundation  construction. 
In  units  of  this  type,  the  combined  shaft  which  carries  the  water 
wheel  and  the  revolving  elements  of  the  generator  and  the  bear- 
ings are  furnished  by  the  builder  of  the  water  wheels.  An  ex- 
ample of  this  type  of  construction  is  illustrated  in  Fig.  31.  The 
wheel  runner  is  of  the  disc  construction  and  is  bolted  against  a 


Fig.  30.  Ideal  Type  of  Small  Horizontal-shaft  Single-overhung  Hydro-electric 
Unit  Arranged  with  Needle-regulating  Auxiliary-relief  Nozzle  with  Direct  Governor 
Control.  Operates  under  300  ft.  (91.5  m.)  effective  head  at  300  r.p.ra.,  developing 
100  hp. 


flange  forged  solid  with  the  water-wheel  generator  shaft.  The 
bearings  are  arranged  to  be  mounted  on  substantial  cast-iron 
base  plates,  which  are  bedded  directly  into  the  concrete  founda- 
tions. This  type  of  construction  is  preferable  on  all  medium  and 
large  sized  units. 

A  single-overhung  hydro-electric  unit  of  the  most  modern 
construction  and  of  large  power  output  is  illustrated  in  Fig.  12. 
This  represents  an  hydraulic  prime-mover  now  under  construc- 


Fig.  31.     Single    Overhung    Horizontal-shaft    Construction.      Wheel    operates    under 
1200  ft.   (366  m.)  effective  head  at  600  r.p.m.,  develojing  1400  hp. 

lion,  mid  has  embodied  in  it  all  of  the  most  recent  developments 
mid  improvements  in  the  art.  In  this  prime-mover  a  single  jet 
of  water  is  applied  to  the  buckets  of  a  single  wheel,  the  wheel 
being  mounted  on  the  extreme  end  of  the  combined  water-wheel 
generator  shaft  and  being  of  disc  construction  bolted  directly 
against  the  Hange  forged  solid  with  the  hollow  chrome-nickel 
steel  oil-tempered  shaft.  The  wheel  construction  shown  in  this 
drawing  is  of  the  double-lug  type,  for  the  reason  that  the  head 
of  water  under  which  it  is  to  operate,  namely,  1650  ft.  (500  m.) 
effective  head — with  a  turning  speed  of  300  revolutions  per  min- 


46 

ute — secures  a  favorable  ratio  between  the  diameter  of  the  power 
jet  and  the  pitch  diameter  of  the  wheel,  so  that  a  thoroughly 
stable  construction  could  be  secured  with  this  type  of  bucket  con- 
struction. Were  the  power  output  of  the  wheel  larger,  it  would 
have  required  the  chain-type  or  triple-lug  construction. 

It  will  be  observed  that  the  servo-motor  controlling  the 
power  output  and  speed  of  the  unit  is  carried  directly  on  the 
power  nozzle,  the  piston  of  the  servo-motor  being  mounted  di- 
rectly on  the  extended  stem  of  the  power  needle;  the  pendulum 
head  and  speed  sensitive  element  with  the  controlling  elements 
are  mounted  on  the  main  nozzle  body.  This  unit  is  arranged  to 
take  pressure  oil  for  operating  the  governor  from  an  independent 
oil-pressure  pumping  system. 

In  addition  to  the  control  by  the  speed  sensitive  element  of 
the  governor,  should  it  be  necessary  or  desirable  at  any  time  to 
control  the  power  output  and  speed  by  hand-regulation,  it  will 
be  observed  that  a  small  valve  with  return  mechanism  is  mounted 
directly  above  the  servo-motor  of  the  governor.  This  valve  is  so 
constructed  with  a  hand  lever  that  the  control  of  the  unit  from 
governor-control  to  hand-control  can  be  instantly  changed  by  a 
single  movement  of  the  lever  operating  a  four-way  valve.  On 
the  top  of  this  four-way  valve,  the  hand-control  valve  is  mounted, 
and  is  so  constructed  that  by  rotating  the  hand-control  wheel, 
through  the  means  of  the  floating  lever,  a  corresponding  setting 
of  the  needle  is  secured.  In  other  words,  if  it  is  desired  to  carry 
a  half  load  on  this  generator,  the  hand  control  valve  can  be  set 
for  half  position.  The  power  needle  will  automatically  come  to 
this  point,  and  will  be  maintained  at  this  position  until  re-set, 
through  the  means  of  the  floating  lever  connections. 

A  further  device  installed  in  the  governor  of  this  unit  is  a 
load-limiting  device,  so  as  to  meet  the  conditions  of  operations  of 
the  power  plant,  the  maximum  amount  of  load  which  the  unit 
can  carry  being  thus  limited.  This  is  of  particular  importance 
during  seasons  of  water  shortage  when  it  is  not  desired  to  have 
the  j ) rime-mover  take  an  excess  quantity  of  water.  The  arrange- 
ment of  the  auxiliary  relief  control  is  secured  through  the  levers 
as  shown  in  the  drawing.  The  water  supplied  to  this  unit  is  con- 
trolled by  a  single- disc  gate  valve  operated  by  a  reversible  water 


47 

motor  with  needle  nozzle  control.  The  construction  of  the  cen- 
trifugal water  disc  and  collar  to  prevent  the  escape  of  splash 
water  from  the  housing,  is  also  illustrated.  At  the  extreme  end 
of  the  shaft  is  located  the  spray  nozzle  for  introducing  cooling 
water  through  the  hollow  shaft,  this  cooling  water  being  drawn 
through  the  shaft  by  the  vacuum  in  the  wheel  housing  and  dis- 
charged into  the  tail-race. 

A  further  improvement  incorporated  in  this  unit,  and  which 
has  proven  to  be  of  great  advantage  in  units  located  in  hot  coun- 
tries, is  the  arrangement  of  the  tail-race  ventilator.  This  device 
is  so  arranged  as  to  take  advantage  of  the  partial  vacuum  that 
exists  in  the  wheel  pit  due  to  the  action  of  the  wheel  as  a  blower 
and  the  ejector  action  of  the  nozzle.  Due  to  this  device,  the  hot 
air  is  drawn  out  of  the  generator  pit  and  discharged  through  the 
tail-race.  This  type  of  unit  is  ideal  in  every  way,  and  is  the 
preferable  one  to  use  wherever  the  conditions  permit  of  its  instal- 
lation. A  number  of  units  of  this  type  of  approximately  10,000 
horsepower  each  have  been  installed,  and  have  proven  to  be 
thoroughly  satisfactory  under  the  severe  conditions  of  regular 
operation.  The  principal  advantages  of  this  type  are  the  highest 
possible  efficiency,  the  simplest  form  of  construction,  with  the 
least  number  of  working  parts  to  take  care  of,  while  the  manner 
of  carrying  the  shaft  gives  assurance  against  the  bearings  wear- 
ing out  of  line  and  causing  trouble.  This  type  is  particularly 
favorable  in  the  total  overall  cost  of  the  installed  equipment,  as 
it  simplifies  the  pipe  fittings  and  connections,  reduces  the  cost  of 
foundation  construction  and  requires  only  a  single  tail-race. 

Where  the  single-overhung  type  can  not  be  constructed  with 
the  power  output  and  speed  desired  with  the  available  water 
pressure,  the  double-overhung  type  is  used ;  this  differs  from  the 
single-overhung  type  in  mounting  a  wheel  on  both  overhanging 
ends  of  the  combined  generator  and  water-wheel  shaft. 

The  double-overhung  type  of  unit  is  likewise  arranged  with 
two  bearings,  the  revolving  element  of  the  generator  being 
mounted  between  the  bearings.  A  single  shaft  is  used,  the  rotor 
of  the  generator  being  located  between  the  bearings,  with  a  wheel 
mounted  on  each  end  of  the  shaft  overhanging  the  bearings. 
Kaeh  wheel  is  driven  by  a  single  jet  of  water.  In  the  largest 


units  it  would  consist  of  a  design  similar  to  that  shown  in  Fig. 
12,  with  a  second  wheel  mounted  on  the  opposite  end  of  the  shaft. 

With  the  double-overhung  type  it  is  possible  to  make  a 
prime-mover  of  double  the  power  output,  maintaining  the  same 
speed  of  rotation,  writh  the  same  conditions  of  water  pressure. 
Where  the  double-overhung  type  is  used  with  automatic  water- 
economizing  nozzles,  it  is  preferable  to  mount  a  separate  gov- 
ernor on  each  nozzle,  and  in  this  way  eliminate  all  long  governor 
rock-shafts  and  connections.  The  double-overhung  type  of  prime- 
mover  has  been  installed  in  a  large  number  of  the  most  import-; 
ant  plants,  with  units  ranging  in  capacity  of  from  12,000  to 
20,000  horsepower. 

In  those  installations  where  the  head  of  water  available  is 
low,  as  compared  with  the  quantity  of  water,  and  where  it  is, 
desired  to  maintain  a  comparatively  high  speed  of  rotation,  mul- 
tiple-jet horizontal-shaft  type  units  have  been  constructed,  and 
such  conditions  are  thoroughly  satisfactory.  In  this  type, 


Fig.  32.  Horizontal-type  Single-overhung  Double- jet  Wheel  with  Auxiliary- 
relief  Nozzle,  and  "Ensign"  Vortex  Baffle  Plate.  This  wheel  operates  under  490  ft. 
(150  m.)  effective  head  at  a  speed  of  300  r.p.m.,  developing  1900  hp. 


49 

usually  two  jets  of  water  are  applied  to  each  wheel  from  the  same 
nozzle  body,  the  jets  being  approximately  90  degrees  apart.  This 
type  has  been  successfully  developed  with  a  single-overhung  hor- 
izontal-shaft unit,  with  two  jets  on  a  single  wheel,  a  unit  of  this 
type  being  illustrated  in  Fig.  32.  In  this  unit  the  power  output 
and  speed  regulation  is  controlled  by  the  governor  operating  the 
needles.  An  auxiliary  relief  nozzle  is  shown  attached  to  one  side, 
discharging  against  an  "Ensign"  vortex  baffle  plate  to  take  up 
the  energy  in  the  jet  from  the  relief  nozzle. 

Where  a  single-overhung  double- jet  unit  will  not  give  the 
power  at  the  desired  speed  under  the  conditions  of  water  pres- 
sure at  the  plant,  a  double-overhung  horizontal-shaft  type  with 
two  jets  on  each  wheel,  making  four  jets  in  all  on  the  unit,  has 
been  developed.  In  this  type  the  needles  controlling  the  jets  to 
the  two  wheels  are  controlled  from  a  central  governor  through  a 
rockshaft  extending  across  the  back  of  the  unit.  On  each  end  of 
this  rockshaft  a  lever  is  mounted  which  operates  the  auxiliary 
relief  nozzle.  For  larger  power  units  than  that  illustrated  in 
Fig.  32,  a  number  of  very  successful  units  have  been  built,  of 
from  11,000  to  15,000  horsepower  each,  using  two  wheels  on  each 
side  of  the  generator,  making  four  wheels  per  unit ;  and  each 
wheel  is  driven  by  two  jets,  thus  making  eight  jets  in  all.  This 
type  is  especially  well  adapted  where  the  water  is  of  such  char- 
acter as  to  be  unsuitable  for  the  pressure  type  of  turbines.  Fur- 
thermore, owing  to  the  high  efficiency  of  the  unit,  and  especially 
due  to  the  flat  efficiency  curve,  it  is  much  more  favorable  for 
overall  twenty-four-hour  water  economy  than  turbines.  In  units 
of  this  type  four  bearings  are  used,  the  rotor  of  the  generator 
being  mounted  between  the  two  main  bearings,  and  at  each  end 
of  the  unit  an  outboard  bearing  is  provided,  the  two  water  wheels 
being  located  on  the  shaft  between  one  main  bearing  and  one 
outboard  bearing.  A  unit  of  this  type  i&  illustrated  in  Fig.  33  ; 
and  Fig.  34  is  a  15,000  horsepower  unit  similar  to  the  one  illus- 
trated in  Fig.  33,  which  represents  a  unit  of  10,500  horsepower. 

General  practice  with  Pelton  hydraulic  prime-movers  has 
been  to  use  the  horizontal  type,  as  it  usually  represents  the  most 
favorable  first  cost  when  taking  into  consideration  the  total  cost 
of  the  plant,  including  the  foundations.  It  further  has  the  ad- 


50 


Pig.  34.  One  of  Four  15,000-lip.  Units,  Horizontal-shaft  Type  with  Four 
Wheels  and  Two  Jets  to  Each  Wheel.  Arranged  with  auxiliary-relief-control  nozzles, 
operating  under  380  ft.  (116  m.)  effective  head  at  200  r.pjn. 

vantage  of  simplicity  of  construction  and  arrangement  of  parts 
available  for  inspection,  lubrication  and  cleaning.  Under  cer- 
tain conditions,  however,  vertical-shaft  types  of  Pelton  hydraulic 
prime-movers  have  been  installed  with  excellent  results  and  favor- 
able first  cost.  This  type  is  especially  suitable  for  comparatively 
low  head  plants,  where  the  water  contains  large  quantities  of 
sand,  grit  or  salt  and  where  pressure-type  turbines  could  not  be 
successfully  operated.  These  vertical-shaft  units  are  usually  ar- 
ranged with  a  wheel  runner  mounted  on  the  lower  end  of  the 
vertical  shaft,  the  entire  weight  of  the  generator  and  the  wheel 
runner  being  carried  on  a  single  thrust  bearing,  the  shaft  being 
further  provided  with  vertical  guide  bearings.  With  prime- 
movers  of  this  type,  six  jets  can  be  installed  on  a  single-wheel 


51 

runner.  Thus  developing  under  a  low  head  a  comparatively 
large  power  output  from  a  single  wheel,  and  at  a  favorable  speed 
of  rotation. 

A  modern  plant  is  illustrated  in  Fig.  35,  this  being  an  in- 
terior of  the  Crane  Valley  No.  1  Plant  of  the  San  Joaquin  Elec- 
tric Light  &  Power  Company.  These  units  are  6000  horsepower 
each,  and  operate  under  1360  ft.  (415  m.)  head  at  400  revolutions 
per  minute.  Four  units  are  installed  in  the  plant.  These  units 


Fig.  35.  Interior  of  the  Crane  Valley  No.  1  Plant  of  the  San  Joaquin  Light 
&  Power  Company,  Containing  Four  6000-hp.  Units.  Operates  under  1360  ft.  (415 
m.)  effective  head  at  400  r.p.m.,  developing  6100  hp.  Power  output  and  speed  con- 
trol being  taken  care  of  by  needle-regulating  auxiliary-relief-control  nozzles. 

are  equipped  with  the  auxiliary  relief-control  nozzles.  It  will  be 
observed  that  the  gate  valves  are  operated  by  hydraulic  cylin- 
ders. These  units  are  of  the  two-bearing  single-overhung  type. 
After  this  plant  was  completed  a  very  careful  efficiency  test  was 
conducted  by  J.  G.  White  &  Company.  Figure  36  shows  thej 
efficiencies  secured  on  this  test.  This  represents  a  characteristic 
curve  from  a  Pelton  wheel. 


52 


1 


C/ 


53 


54 

In  conducting  this  test,  as  it  was  only  possible  to  segregate 
the  actual  electrical  losses,  and  as  there  were  no  means  for  seg- 
regating the  windage  and  friction  of  the  generator,  these  latter 
losses  are  included  in  the  efficiency  curve. 

The  most  recent  plant  is  the  Drum  Power  Plant  of  the  Pa- 
cific Gas  and  Electric  Company,  this  being  illustrated  in  Fig.  37. 
In  this  plant  are  at  present  installed  two  hydro-electric  units, 
double- overhung  type,  of  20,000  horsepower  output  each,  operat- 
ing under  1330  ft.  (445  m.)  head  at  360  revolutions  per  minute. 
The  wheels  are  of  the  chain-type  construction  illustrated  in  Fig. 
4.  This  plant  is  equipped  with  needle-regulating  deflecting  noz- 
zles, the  regulating  needles  being  equipped  with  remote  electric- 
motor  control  from  the  switchboard. 

The  reason  for  adopting  the  needle-regulating  deflecting 
nozzles  in  this  plant  was  due  to  the  fact  that  six  power  plants  in 
scries  will  be  installed,  taking  water  from  the  same  source  of 
supply.  As  there  were  not  available  sites  in  the  canyon  through 
which  the  water  canal  is  carried  to  install  regulating  reservoirs, 
it  was  necessary  to  arrange  a  system  of  control  which  would  per- 
mit of  now  of  water  to  the  lower  plants  without  momentary 
interruption.  When  this  plant  is  completed,  it  will  include  four 
20,000  horsepower  units. 

An  illustration  of  the  adaptation  of  the  Pelton  wheel  to  a 
modern  mining  plant  is  illustrated  in  Fig.  38,  which  shows  the 
interior  view  of  the  power  plant  of  the  Granby  Consolidated 
Mining,  Smelting  &  Power  Company,  Anyox,  B.  C.  In  this  plant 
Pel  ton  wheels  are  connected  to  a  large  piston  blowing-engine,  a 
lar»v  piston  air-compressor,  to  three  rotary  air-blowers  of  the 
Connersville  type,  and  also  to  the  electric  generators  and  excit- 
ers for  the  electrolytic  process. 

It  has  been  the  intent  of  this  paper  to  submit  briefly  to  the 
interested  engineer  the  principal  types  of  prime-movers  that 
have  been  developed,  with  their  methods  of  regulation,  and  only 
those  types  have  been  described  and  illustrated  which  have 
proven  thoroughly  reliable  and  satisfactory  under  the  severe  con- 
ditions of  regular  service  operation.  The  art  is  one  that  is  con- 
stantly developing.  The  limitations  as  to  power  output  and 
speed  have  not  as  yet  been  reached  and  are  only  limited  by  the 


55 


Fig.  38.  Interior  of  a  Modern  Mining  Plant,  the  Granby  Consolidated  Mining. 
Smelting  &  Power  Company,  Anyox,  B.  C. 

The  plant  consists  of  three  water  wheels  connected  to  rotary  air  blowers  of  the 
Connersville  type,  each  wheel  developing  775  hp.  under  374  ft.  (114  m.)  effective 
head,  at  115  r.p.m. 

Two  water-wheel  generator  units,  each  wheel  developing  1400  hp.  under  370 
ft.  (113  m.)  effective  head  at  400  r.p.m. 

One  water  wheel  for  motor-generator  set,  developing  75  hp.  under  370  ft. 
(113  m.)  effective  head,  at  900  r.p.m. 

One  water  wheel  for  Connersville  blowing  engine,  developing  1400  hp.  under 
374  ft.  (114  m.)  effective  head  at  75  r.p.m. 

One  water  wheel  for  Nordberg  air  compressor,  wheel  developing  800  hp.  under 
374  ft.  (114  m.)  effective  head  at  84  r.p.m. 

necessities  of  the  particular  installation.  As  to  the  limits  of  ca- 
pacity, they  are  restricted  only  by  the  profitable  demand  for  the 
power  and  by  the  quantity  and  head  of  water  available ;  the  only 
practical  limitations  as  to  the  head  or  pressure  under  which  a 
power  plant  can  be  constructed,  is  the  cost  of  the  pressure  pipe 
line. 

Plans  have  been  developed  which  demonstrate  that  an 
hydraulic  prime-mover,  thoroughly  satisfactory  from  the  stand- 
point of  first  cost,  upkeep  and  reliable  operation,  can  be  con- 
structed for  heads  in  excess  of  6000  ft.  in  a  single  drop,  and  in 


56 

units  as  large  as  30,000  horsepower  each,  the  limitations  being 
the  question  of  the  cost  and  the  difficulties  of  securing  a  satis- 
factory pressure  pipe  line,  an  available  source  of  water  supply 
which  can  be  developed  at  a  reasonable  cost,  and  a  satisfactory 
market  for  the  power  generated.  Other  than  this,  the  results  to 
bo  secured  from  units  of  this  capacity  and  operating  under  these 
conditions  would  be  absolutely  satisfactory  in  regular  operating 
service.  It  is  not  predicted  that  this  represents  the  limit  of  ca- 
pacity or  head.  It  would  indicate,  however,  the  approach  to  a 
limit,  as  representing  possibly  the  maximum  conditions  of  a  reli- 
able water  supply  that  can  be  secured  within  a  reasonable  cost  of 
development  and  within  a  reasonable  distance  of  a  profitable 
market. 

The  several  illustrations  which  have  been  introduced  in  this 
paper  have  been  selected  from  regular  shop  photographic  record 
prints  as  being  the  best  means  of  illustrating  the  general  develop- 
ment of  the  art  and  improvements  in  the  details  of  construction 
and  in  the  systems  of  regulation,  and  from  this  standpoint  will 
be  of  interest  to  engineers. 

The  efficiency  to  be  secured  from  an  Impulse  Prime-Mover 
is  affected  by  the  type  of  the  unit,  the  head  or  pressure  that  it  is 
to  operate  under,  and  the  speed  of  rotation ;  these  factors  deter- 
mining the  ratio  of  the  jet  and  the  pitch  diameter  of  the  wheel. 

A  characteristic  efficiency  curve,  showing  the  results  from  a 
medium  sized  prime-mover  under  actual  operating  conditions,  is 
shown  in  the  efficiency  curve  of  the  Crane  Valley  No.  1  Power 
Plant,  Fig.  36. 

Under  exceptionally  favorable  conditions  the  efficiency  of  a 
Pelton  hydraulic  prime-mover  will  range  between  83%  and  86%, 
depending  upon  the  special  limitations  of  the  installation.  It  is 
anticipated  that  these  extremely  favorable  efficiencies  will  be 
somewhat  improved,  and  with  heads  in  excess  of  3000  ft.  with 
large  sized  power  units,  it  is  reasonable  to  predict  an  efficiency 
of  approximately  90%. 

In  considering  these  questions  of  efficiency,  it  must  be  appre-. 
ciated  that  they  are  based  upon  the  prime-movers  installed  in. 
actual  operating  plants  and  on  the  basis  of  regular  commercial 
service,  and  represent  the  total  overall  efficiency  of  the  prime- 
mover. 


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